20, 3 McLean and Lee: The Citrus-canker Organism 311 
of air from the suction system into the aspirator being controlled 
by a screw pinchcock (see fig. 1). The operation of the appa- 
ratus was very simple. Mercury was sucked up into the aspi- 
rator tube, with the screw pinchcock closed. The suction tube 
was then closed at the bottom by a pinchcock, and the screw cock 
Screw 
pinchcock 
Aspirator tube 
uction tube 
| Pinchcock 
Rubber cushion 
anker bacteria in water 
Fic, 1. Apparatus used to inject leaves with citrus-canker organisms, 
184895-—_-6 
